Cooling system for shafts and the like



1967 E. w. BULLOCK COOLING SYSTEM FOR SHAFTS AND THE LIKE Filed April29, 1965 INVENTOR. E/Z ZS M Bil/lack %447 4/M A f/omgys United StatesPatent 3,297,239 COOLING SYSTEM FOR SHAFTS AND THE LIKE Ellis W.Bullock, Birmingham, Ala., assignor to The Fly Ash Arrestor Corporation,a corporation of Alabama Filed Apr. 29, 1965, Ser. No. 451,899 Claims.(230128) system of the character designated which reduces linear shaftexpansion to a minimum thus permitting improved coupling clearances,which results in improved performance with reduced maintenance andlonger coupling life.

A further object of my invention is to provide a cooling system of thecharacter designated which eliminates the necessity of providing aturning gear to keep the assembly from being in a static condition whenthe assembly is stopped under temperatures high above ambient.

A further object of my invention is to provide a cooling system of thecharacter designated which shall be simple of construction, economicalof manufacture and one which includes improved means for circulatingcooling air around the shaft and hub of a fan or blower handling hotgases, which shall be effective to cool the shaft and hub withoutunnecessarily diluting and cooling the gases being handled.

Heretofore in the art to which my invention relates, various means havebeen devised for cooling the shaft of a blower or fan handling hotgases. It has been proposed to introduce cooling air between a shaft anda sleeve by drawing all of the cooling air in through passageways at theend of the sleeve. Also, the use of various liquids, such as water, oiland the like have been proposed for cooling the shaft of a blowerhandling hot gases. Such methods of cooling shafts have proved to beentirely unsatisfactory due to the difliculties encountered in handlingthe various liquids.

To overcome the above and other difficulties, I provide means forcooling the shaft of a centrifugal blower by providing a sleeve whichsurrounds the blower shaft whereby air is induced through the spacebetween the sleeve and the shaft by the partial vacuum created by thecentrifugal blower. Instead of providing an air inlet at the outer endof the sleeve for introducing all of the cooling air, I provide an airblower which is in communication with the outer end of the sleevewhereby cooling air is forced between the sleeve and the shaft upon anincrease in pressure within the intake side of the centrifugal blower,such as would occur when the centrifugal blower is stopped. That is, thecooling air is drawn through the blower into the space between the shaftand the sleeve so long as there is a negative pressure between thesleeve and the shaft. Also, I provide means for deenergizing the coolingair blower when the temperature of the gas being conveyed through thecentrifugal blower decreases to a predetermined point. One end of thesleeve surrounding the shaft communicates with a conical member whichflares outwardly toward the impeller whereby the cooling air passesadjacent the impeller hub and then it is drawn outwardly by theimpeller.

Apparatus embodying features of my invention is illustrated in theaccompanying drawing, forming a part of this application, in which:

FIG. 1 is an elevational view partly in section, showing a conventionalcentrifugal blower having my invention incorporated therein;

' like.

ICC

FIG. 2 is an enlarged, elevational view, partly in section, showing oneside of the apparatus shown in FIG. 1; and

FIG. 3 is a fragmental, sectional view taken generally along the line 33of FIG. 1.

Referring now to the drawing for a better understanding of my invention,I show a centrifugal blower having a casing 10 with two inlet chambers11 and 12 at each side thereof. The centrifugal blower is provided withan outlet 13 and an impeller housing 14. The inlet chambers 11 and 12communicate with the impeller housing by conical members 16 which aretapered inwardly toward the impeller housing, as shown. Extendingthrough the inlet chambers 11 and 12 and the impeller housing 14 is ashaft 17 which is mounted in suitable bearings 18 which, in turn, aresupported on pedestals 19, as shown. Mounted within the impeller housing14 is an impeller having blades 21 supported by a central plate 22 andhub members 23 mounted on the shaft 17.

The apparatus described hereinabove is conventional for blowers whichhandle hot gases from furnaces and the My improved apparatus embodiesthe means for cooling the shaft 17 and the hub 23 to overcome expansionand balance problems encountered with high temperature conditions.

Surrounding the shaft 17 at each side of the plate 22 is a coolingsleeve 24. As shown in FIG. 2, each sleeve 24 surrounds the shaft 17with a relatively close clearance and extends from a point adjacent theouter side of its associated inlet chamber to a point adjacent the hub23. The outer end of each sleeve 24 is secured to the outer wall of theinlet chambers 11 and 12 by suitable means, such as bolts 26.

Communicating With each sleeve 24 adjacent the outer end thereof is oneend of a conduit 27. The other end of the conduit 27 is connected to thedischarge side of an air blower indicated generally at 28. Where thecentrifugal blower is employed to convey gases at extremely hightemperatures, the cooling sleeve 24 and the conduit 27 are surrounded bya suitable insulating material indicated generally at 29 in order tokeep the cooling air requirement at a minimum,

The inner end of each sleeve 24 is connected to a cone-shaped member 31which flares outwardly toward the plate 22, as shown in FIG. 2, Thecone-shaped members 31 may be formed integrally with the sleeves 24 ormay be secured thereto by suitable means. Each cone member 31 is spacedfrom the plate 22, as shown in FIG. 2, to provide an air passageway 32therebetween.

Mounted at each side of the plate 22 inwardly of the impeller blades 21is an annular row of cooling air vanes 33 which serve as radiation finsand also as small fan blades that assist in producing the necessary flowof cooling air between the sleeve 24 and the shaft 17. The cone members31 are also surrounded by the insulation material 29, as shown.

The intermediate portion of each sleeve 24 is supported by radiallyextending bars 34 which are connected at their outer ends to the conicalmembers 16 of the centrifugal blower. The inner ends of the bar 34 maybe connected to an annular member '36 which surrounds the insulationmaterial 29 carried by the sleeves 24. Each annular member 36 is adaptedfor sliding movement relative to the insulation material 29 to permitexpansion and contraction of the sleeve 24 in response to changes intemperatures.

Mounted within each intake chamber 11 and 12 is the sensing element of apressure switch 37 which is operatively connected to the cooling airblower 28 by :a line 38. The pressure switch 37 is designed to energizethe cooling air blower when the pressure Within the intake chambers 11and 12 is reduced to a predetermined amount, such as occurs when thecentrifugal blower is stopped. Also mounted within, each intake chamber11 and 12 is the sensing element of a thermal switch 39 which isoperatively connected to the blower 28 by a line 41. The pressure switch37 and the thermal switch 39 are connected to each other in serieswhereby they are both in circuit with the cooling air blower 28 by thelines 38 and 41.

From the foregoing description, the operation of my improved coolingsystem for shafts and the like will be readily understood. When thecentrifugal fan unit is Operating in a manner to create a negative inletpressure and a slight positive discharge pressure, the negative pressureproduced by the impeller blades 21 in addition to the negative pressureproduced by the venturi effect resulting from gas flow over the coolingsleeve cone and in addition to the fan effect of the cooling air vanes33 causes an air flow through the space defined between the sleeve 24and the shaft 17. The cooling air is thus drawn inwardly through thecooling air blower 28 whereupon it passes through conduit 27 into sleeve24 whereupon it flows in the direction of the arrows shown in FIG. 2 andis finally discharged through the passageways 32 defined between theconical members 31 and the plate 22. As the air passes between thesleeve 24 and the shaft 17, the shaft 17 is cooled. Also, the passage ofthe air adjacent the hub 23 cools the hub prior to discharge of the airinto the impeller housing. So long as the centrifugal blower isoperating with a negative intake pressure and a slight positivedischarge pressure, it is not necessary for the cooling air blower 28 tobe operating while the centrifugal fan unit is running. In actualpractice, I find that suflicient fiow of outside air is induced throughthe blower 28, conduit 27 and sleeve 24 to maintain the temperature ofthe shaft 17 and the hub 23 below 125 F; even though the temperature ofthe gases being conveyed by the centrifugal blower is in excess of 1000F.

When the centrifugal blower unit stops for any reason, the pressureswitch 37 energizes the cooling air blower 28 which supplies sufiicientair through the cooling sleeve 24 to maintain the temperature of theshaft and the hub below the 125 F. maximum temperature. When theinternal temperature of the intake chambers 11 and 12 reaches a pointthat is F. above outside temperature, the thermal switch 39 deenergizesthe air cooling blower 28. That is, when the temperature of the gasesbeing conveyed by the centrifugal blower unit are lowered sufi'icientlyto bring about a reduced internal temperature within the intake chambers11 and 12 which is 10 F. above outside temperature, the thermal switch39 is moved to open position to thereby deenergize the cooling airblower 28.

When the centrifugal blower unit is operating with positive pressure onthe blower discharge, no cooling air is drawn inwardly between thesleeve 24 and the shaft 17. However, since the pressure switch 37energizes the cooling air blower 28 when there ceases to be a negativepressure within the intake chambers 11 and 12, the cooling air blowers28 would be energized to thus supply sufiicient cooling air to maintainthe shaft 17 and the hub 23 at the desired, reduced temperature. Sincethe thermal switch 39 is connected in series with the pressure switch37, the cooling air blower 28 is not energized until the fan reaches itsfull speed whereby the internal temperature of the intake chambers 11and 12 would be greater than 10 above the outside temperature. Also,while operating the centrifugal blower under positive pressures, thepressure switch 37 would cause the cooling air blower 28 to continueoperation after shut-down until the internal temperature of the intakechambers 11 and 12 reached a point that is 10 above outside temperature.

The shaft 17 for the centrifugal blower is subject to deflection due toa concentrated weight from the impeller in addition to a deflection dueto a uniform loading of its own weight. These deflections determine thecritical speed or frequency of the shaft. When the centrifugal blowerunit is operating the deflections result in rapidly changing stressreversals that have no effect on the balance of the assembly in aproperly designed and balanced unit. However, if the unit is stoppedunder high temperatures above ambient temperature and allowed to cool toambient temperature in a static condition, there occurs stressconcentrations that cause a temporary shaft distortion. This results insuflicient eccentricity of motion to cause a serious imbalance of theassembly. With small, high speed units having small deflections, thevibration from distortion is not of sufiicient amplitude to cause asafety problem. The unbalanced condition will disappear within twenty tothird minutes of operation under a stabilized temperature condition.With large units, on the other hand, the starting vibration will exceedreasonable safe limits and in order to prevent the stress concentrationsthat cause a serious imbalance condition, it is necessary to provide aturning gear to keep the assembly from being in a static condition whilethe assembly is allowed to cool to ambient temperature. It will thus beseen that maintaining the shaft and hub at low temperatures minimizesexcessive stress concentrations and on a properly designed uniteliminates the necessity for a turning gear. Also, maintaining the shaftand hub cool at all times prevents serious imbalance from thermal shockresulting from a quick, high temperature rise on a cold assembly.

From the foregoing, it will be seen that I have devised an improvedcooling system for shafts and the like. By maintaining the shaft and hubcool at all times I not only eliminate serious imbalance conditions buteliminate all problems of the impeller and hub becoming loose on theshaft. Also, I reduce linear shaft expansion to a minimum thuspermitting better coupling clearances which result in improvedperformance with reduced maintenance and longer coupling life.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In a centrifugal blower having a lateral inlet chamber, an outlet, animpeller and a rotatable impeller shaft extending through the inletchamber, means for cooling the impeller shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaftwith one end of the sleeve extending to a point adjacent the Outer sideof the inlet chamber and the other end thereof terminating adjacent theimpeller to define a passageway between said sleeve and said shaft forthe passage of cooling air,

(b an air blower communicating with said sleeve adacent said one endthereof and disposed to supply cooling air to said sleeve, and

(c? means to energize and deenergize said air blower 111 response topredetermined variations in temperature or pressure within thecentrifugal blower,

2. In apparatus as defined in claim 1 in which an in. sulatron materlalsurrounds the sleeve to reduce the cooling an requirements where thecentrifugal blower is emp yed to convey gases at extremely hightemperatures.

3. In apparatus as defined in claim 1 in whi h id other end of thesleeve flares outwardly within the i peller.

4. In apparatus as defined in claim 1 in which a conduit communicatessaid air blower with said one end of the sleeve.

5. In apparatus as defined in claim 4 in which the conduit extendsthrough the inlet chamber and is surrounded by an insulating material.

6. In a centrifugal blower embodying a lateral inlet chamber, an outlet,and impeller blades carried by a plate which is secured to a hub mountedon a shaft extending through the inlet chamber, means for cooling theshaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaftwith one end of the sleeve extend- 1 ing to a point adjacent the outerside of the inlet chamber and the other end thereof terminating inspaced relation to the hub to define a passageway between said sleeveand said shaft for the passage of cooling air,

(b) a conical member communicating with said other end of the sleeve andflaring outwardly toward and in spaced relation to said plate to definea passageway therebetween for exhausting cooling air which is conveyedthrough said sleeve and said conical member,

(c) an air blower communicating with said sleeve adjacent said one endthereof and disposed to supply cooling air to said sleeve, and

((1) means to energize and deenergize said air blower in response topredetermined variations in temperature or pressure within thecentrifugal blower.

7. In apparatus as defined in claim 6 in which the conical member isformed integrally with said sleeve.

8. In apparatus as defined in claim 6 in which the conical member issurrounded by an insulating material.

9. In apparatus as defined in claim 6 in which angularly spaced vanesare carried by said plate inwardly of said impeller blades in positionto provide radiation fins and draw cooling air outwardly of said conicalmember.

10. In apparatus as defined in claim 6 in which the sleeve is supportedintermediate its ends by radially extending bars which are connected attheir outer ends to portions of the centrifugal blower.

11. In a centrifugal blower having a lateral inlet chamber, an outlet,an impeller and a rotatable impeller shaft extending through the inletchamber, means for cooling the impeller shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaftwith one end of the sleeve extending to a point adjacent the outer sideof the inlet chamber and the other end thereof terminating adjacent theimpeller to define a passageway between said sleeve and said shaft forthe passage of cooling a1r,

(b) an air blower communicating with said sleeve adjacent said one endthereof and disposed to supply cooling air to said sleeve, and

(c) means to energize said air blower upon an increase in pressurewithin the centrifugal blower above a predetermined amount and upon anincrease in internal temperature of the centrifugal 5 blower above apredetermined amount to force cooling air through said sleeve.

12. In a centrifugal blower having a lateral inlet chamber, an outlet,an impeller and a rotatable impeller shaft extending through the inletchamber, means for cooling the impeller shaft comprising:

(a) a sleeve surrounding and in closely spaced relation to the shaftwith one end of the sleeve extending to a point adjacent the outer sideof the inlet chamber and the other end thereof terminating adjacent theimpeller to define a passageway between said sleeve and said shaft forthe passage of cooling air,

(b) an air blower communicating with said sleeve adjacent said one endthereof and disposed to supply cooling air to said sleeve, and

(c) a pressure switch having a sensing element within the centrifugalblower and operatively connected to said air blower to energize said airblower when the pressure at the receiving side of the centrifugal blowerincreases to a predetermined amount, and

(d) a thermal switch having a sensing element within gas being conveyedby the centrifugal blower.

References Cited by the Examiner UNITED STATES PATENTS 100,238 2/1870Sturtevant 230209 2,755,989 7/1956 COWfil'd 230-128 FOREIGN PATENTS149,509 11/1931 Switzerland.

MARK NEWMAN, Primary Examiner.

F. RADUAZO, Assistant Examiner.

1. IN A CENTRIFUGAL BLOWER HAVING A LATERAL INLET CHAMBER, AN OUTLET, ANIMPELLER AND A ROTATABLE IMPELLER SHAFT EXTENDING THROUGH THE INLETCHAMBER, MEANS FOR COOLING THE IMPELLER SHAFT COMPRISING: (A) A SLEEVESURROUNDING AND IN CLOSELY SPACED RELATION TO THE SHAFT WITH ONE END OFTHE SLEEVE EXTENDING TO A POINT ADJACENT THE OUTER SIDE OF THE INLETCHAMBER AND THE OTHER END THEREOF TERMINATING ADJACENT THE IMPELLER TODEFINE A PASSAGEWAY BETWEEN SAID SLEEVE AND SAID SHAFT FOR THE PASSAGEOF COOLING AIR, (B) AN AIR BLOWER COMMUNICATING WITH SAID SLEEVEADJACENT SAID ONE END THEREOF AND DISPOSED TO SUPPLY COOLING AIR TO SAIDSLEEVE, AND (C) MEANS TO ENERGIZE AND DEENERGIZE SAID AIR BLOWER INRESPONSE TO PREDETERMINED VARIATIONS IN TEMPERATURE OR PRESSURE WITHINTHE CENTRIFUGAL BLOWER.